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Initial revision

/*
 * Copyright (C) 2017 Aaron M. D. Jones <aaronmdjones@gmail.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following
 * conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED.
 *
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "acopm-common.h"

#include <errno.h> /* errno */
#include <fcntl.h> /* open(), O_* */
#include <string.h> /* strerror() */
#include <unistd.h> /* chdir(), exit(), fork(), pipe(), setsid() */

#include <event2/event.h> /* event_reinit(), struct event_base */

#include "daemon.h" /* decls for own functions */
#include "vars.h" /* extern struct event_base *ev_base */

#include "utils/log.h" /* acopm_log_*() */

static bool acopm_do_daemon = false;

static inline bool acopm_attr_inline
acopm_daemon_child(const int pipefd)
{
	bool result = false;
	const unsigned char buf = 0x01;
	const int nullfd = open("/dev/null", O_RDWR | O_NOCTTY);

	if (nullfd == -1)
	{
		(void) acopm_log_error("%s: open: %s", __func__, strerror(errno));
		goto end;
	}

	if (event_reinit(ev_base) == -1)
	{
		(void) acopm_log_error("%s: event_reinit: %s", __func__, strerror(errno));
		goto end;
	}

	if (chdir("/") == -1)
	{
		(void) acopm_log_error("%s: chdir: %s", __func__, strerror(errno));
		goto end;
	}

	for (int x = 0; x < 3; x++)
		if (x != nullfd)
			(void) dup2(nullfd, x);

	if (nullfd >= 3)
		(void) close(nullfd);

	if (setsid() == -1)
	{
		(void) acopm_log_error("%s: setsid: %s", __func__, strerror(errno));
		goto end;
	}

	if (write(pipefd, &buf, sizeof buf) == -1)
	{
		(void) acopm_log_warning("%s: write: %s", __func__, strerror(errno));
		(void) acopm_log_warning("%s: our parent may think we died!", __func__);
	}

	result = true;

end:
	(void) close(pipefd);
	return result;
}

void
acopm_daemon_set(void)
{
	acopm_do_daemon = true;
}

bool
acopm_daemonise(void)
{
	if (! acopm_do_daemon)
		return true;

	(void) acopm_log_flush();

	int pipefd[2];

	if (pipe(pipefd) == -1)
	{
		(void) acopm_log_error("%s: pipe: %s", __func__, strerror(errno));
		return false;
	}

	const pid_t ret = fork();

	if (ret == -1)
	{
		(void) acopm_log_error("%s: fork: %s", __func__, strerror(errno));
		return false;
	}
	else if (ret == 0)
	{
		(void) close(pipefd[0]);
		return acopm_daemon_child(pipefd[1]);
	}
	else
	{
		unsigned char buf = 0x00;

		(void) close(pipefd[1]);

		if (read(pipefd[0], &buf, sizeof buf) <= 0)
			exit(EXIT_FAILURE);

		exit(EXIT_SUCCESS);
	}
}